Abstract: Grinding forces are composed of chip formation forces and friction forces. Based on this concept, we obtain a new grinding force model. It is composed of two terms coaresponding to chip formotion forces and friction forces respectively. Relationships between grinding forces and grinding parameters with workpieces of different meterials are determind experimentally. The results indicate a close agreement with" the model proposed. We have also analysed the ratio between tangential forces and normol forces with respect to both chip formation forces and friction forces. The ratio generally falls within the range of 0.2~0.59. When worpieces of different meterials are grinded, the measured values of the ratio are within this range. Based on the grinding force model obtained, problems such as the significance of equivalent chip thickness and the effect of high speed grinding are discussed.